AppNexus parsing/handing bid request works; new version of realtime-bidding.proto
parsing ok. (both mobile and single tag BR)
answers: no_bid to requests sent by AppNexus; need to beef up the response -> done
adding creative compatibility check
adding support for providerConfig. support for membership and excluded attributes;
fixed test
Merge branch 'APPNEXUS' of https://github.com/jsulmont/rtbkit into jsulmont-APPNEXUS